Re: [PATCH net-next] candev: allow SJW user setting for bittiming calculation
From: Wolfgang Grandegger <hidden>
Date: 2011-09-22 11:00:19
Hi Oliver, On 09/22/2011 12:24 PM, Oliver Hartkopp wrote:
quoted hunk
This patch adds support for SJW user settings to not set the synchronization jump width (SJW) to 1 in any case when using the in-kernel bittiming calculation. The ip-tool from iproute2 already supports to pass the user defined SJW value. The given SJW value is sanitized with the controller specific sjw_max and the calculated tseg2 value. As the SJW can have values up to 4 providing this value will lead to the maximum possible SJW automatically. A higher SJW allows higher controller oscillator tolerances. Signed-off-by: Oliver Hartkopp <redacted> ---diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c index 9bf1116..25695bd 100644 --- a/drivers/net/can/dev.c +++ b/drivers/net/can/dev.c@@ -150,7 +150,19 @@ static int can_calc_bittiming(struct net_device *dev, struct can_bittiming *bt) bt->prop_seg = tseg1 / 2; bt->phase_seg1 = tseg1 - bt->prop_seg; bt->phase_seg2 = tseg2; - bt->sjw = 1; + + /* check for sjw user settings */ + if (!bt->sjw || !btc->sjw_max) + bt->sjw = 1; + else { + /* bt->sjw is at least 1 -> sanitize upper bound to sjw_max */ + if (bt->sjw > btc->sjw_max) + bt->sjw = btc->sjw_max; + /* bt->sjw must not be higher than tseg2 */ + if (tseg2 < bt->sjw) + bt->sjw = tseg2; + } +
Hm, bt->sjw is always 0 when can_calc_bittiming() is called!? Or have I missed something. Wolfgang,